1. Field of the Invention
The present invention relates to an interconnector to electrically connect a plurality of electronic device elements in a serial direction or a parallel direction. Particularly, the present invention relates to a planar type interconnector employed in the connection of solar cells for artificial satellites or diodes, a method of forming such an interconnector, and a join apparatus thereof.
2. Description of the Background Art
The current consumed energy worldwide corresponds to an enormous amount, which is mainly supplied by fossil fuel such as oil or the like. It is expected that the fossil fuel will be exhausted in the near future if the energy consumption increases at the current rate.
In these few years, intensive research of the technology utilizing inexhaustible and clean solar energy has been in progress as the energy source to replace the fossil fuel. Development of solar cells can be referred to as one major technique thereof. In general, the plurality of solar cells constituting the solar battery are arranged adjacent to each other. An interconnector formed of a small piece of metal is provided in order to electrically connect the solar cells in the serial or parallel direction.
An interconnector includes a stress relief portion that absorbs displacement generated between solar cells connected to each other, and at least two connecting portions connected to the solar cells. The invention disclosed in Japanese Patent Laying-Open No. 4-298082 and the invention disclosed in Japanese Utility Model Laying-Open No. 1-125563 can be enumerated as conventional art related to such an interconnector.
FIG. 1A schematically shows a structure of an interconnector disclosed in Japanese Patent Laying-Open No. 4-298082. This interconnector 101 includes a front surface electrode connecting portion 121, a back electrode connecting portion 122, and a stress relief portion 110. As shown in FIG. 1B, front surface electrode connecting portion 121 and back electrode connecting portion 122 have a mesh structure.
The interconnector disclosed in Japanese Utility Model Laying-Open No. 1-125563 includes a first stress absorption portion having a plurality of permeable holes arranged in the row direction with respect to the interconnector, and a second stress absorption portion having a plurality of permeable holes arranged in the column direction.
In order to withstand the displacement generated between adjacent solar cells, an area for connecting or welding sufficient for the connecting portion is required in joining the connecting portion of the interconnector with the electrode portion of the solar cell. In the inventions disclosed in the aforementioned Japanese Patent Laying-Open No. 4-298082 and Japanese Utility Model Laying-Open No. 1-125563, a mesh opening or permeable hole is provided at the connecting portion of the interconnector. Connection with the electrode portion of the solar cell was effected using the opening or permeable hole. In order to ensure a connection area sufficient for the connecting portion of the interconnector, the area of the connecting portion of the interconnector will become larger. In solar cells for artificial satellites, there is a problem that increase in the area of the connecting portion will raise the cost since noble metal such as gold, silver or the like is generally used as the material of the interconnector. Increase in the area of the connecting portion of the interconnector will also reduce the light-receiving area of the solar cell. As a result, there is a problem that the efficiency and output of the solar cell will be degraded.
The provision of a mesh opening or permeable hole at the connecting portion of the interconnector will become the cause of crushing the mesh opening or permeable hole when welding is effected using a weld electrode of a large width. When pressure is applied with the weld electrode in contact with the residual portion of the mesh opening or permeable hole, i.e. the remaining metal portion for welding, stress concentration occurs at that portion to become the cause of damaging the solar cell. For the reliability of the weld portion, welding was effected on one connecting portion between the interconnector and the solar cell using a small weld electrode of a small width. If the area of the connecting portion of the connector is increased, welding must be effected many times on one connecting portion when a small weld electrode is used. A tremendous amount of time will be required for welding to degrade the productivity.
There was also problem that the process of etching is required to form the mesh opening or permeable hole at the connecting portion of the interconnector, resulting in increase of the processing cost. In the case where etching is applied on the connecting portion of the interconnector, automation cannot be facilitated since it is extremely difficult to work on components of a continuous form. Even if a continuous interconnector is formed by working on a continuous form, there was a problem that the cost of the interconnector is increased.
In the case where a continuous interconnector cannot be formed, each produced interconnector must be accommodated in a pallet or the like individually. Extra space to install the pallet is required. There is also the possibility that the produced interconnector may be lost if small in size.